Aromatic polyamides prepared from aromatic diamines and aromatic dicarboxylic acids or chlorides thereof are now under extensive investigation because of their excellent heat resistance and flame retardance. However, aromatic polyamides generally have a high melting points and, in air, many aromatic polyamides have a melting point higher than the thermal decomposition temperature. Thus, it is difficult for the aromatic polyamides to be injection molded or extrusion molded. Moreover, the solubility of aromatic polyamides in the conventional organic solvents is poor and many difficulties are encountered in producing fibers, films, coatings or the like using the aromatic polyamides. Such poor moldability is now improved by lowering the melting point of the aromatic polyamides by using as copolymers or by dissolving them in specific solvents.
Various methods have been proposed to produce aromatic polyamides having improved moldability, which include (a) a method for copolymerizing an aliphatic component (Japanese Pat. application (OPI) Nos. 109592/77 and 94397/78 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), (b) a method for introducing connecting functional groups into the main chain, thereby providing flexibility (U.S. Pat. No. 3,505,288, Japanese Pat. application (OPI) Nos. 23198/77 and 104695/78), and (c) a method for random copolymerizing an aromatic component (Japanese Pat. application (OPI) Nos. 104697/78 88427/81, and U.S. Pat. No. 4,410,684). However, polyamides produced by the above methods do not have a sufficient balance between the moldability and the heat resistance.